Hi guys as title suggests I have a pi 4b 4gb and basically I want to connect it to my isp provided router (wired connection via a lan cable) and run an openvpn config on it and then connect it to an access point that i already have (this one is wired too via a usb to RJ45 adapter and lan cable). I know that I need to flash openwrt image on an sdcard and install it on pi4 but I don't know how to configure openwrt after that and honestly the guides on the forums and internet are a little confusing (I'm not that tech savy) also I read that not all usb to RJ45 adapters work with openwrt on pi4 but I don't know which one to buy. can anyone show me a fool proof guide or tell me what I need to do? Edit: thank you all amazing people for your input I found a Google wifi mesh solution second hand (ac-1304 model) that is supported by OpenWRT latest firmware for a good price and I went with that. Gonna find a proper use case for my Raspberry Pi in the future for now gonna keep it as a tinkering device.
You're not going to have fun when using OpenVPN. Even Wireguard will be a stretch. The Raspberry Pi does not have any hardware cryptography acceleration built-in and the raw compute power is very limited.
Ran WireGuard on a Pi1 and it was fine for two users. Albeit WireGuard was the ONLY thing running aside from a Gitlab Runner.
A 4b should be more than enough for many use cases except things that cause torrents of packets - but even then YMMV. It really depends on the workload.
One bit of advice: if you can, use a storage device other than the micro-sd slot for the 4B. Again YMMV.
Computing power isn't just a general quantity. Networking devices have dedicated chips in them to perform various parts of processes. (Encryption, decryption, encoding, decoding, compression, decompression, etc.)
That's hardware acceleration. There are chips that are super efficient and powerful but they can only do that one thing.
That's fine if you know exactly what the device is going to be for, so you can put in the exact chips it needs to do only what it needs to do.
This may be helpful if you haven't found it yet. It has a full list of instructions to flash and configure openwrt on the rpi 4 with wireguard VPN. It says you can also do it with openvpn, but claim the speed was much slower.
If it's inadequate then i'd recommend a used fanless thin-client type PC, such as a Wyse 5070, just make sure it comes with PSU and a few GB of RAM and SSD. And check reports of how much power it uses at idle.
Usually they're normal x86 PCs with nothing unusual about them so just your Linux/BSD distro of choice.
You can look up the processor model to see what crypto acceleration it can do, or see if there's any wireguard benchmarks available.
Some have interesting processors like PowerPC, or other strange hardware, but avoid them unless interesting is what you're after.
Can you just get your own Router and use that instead of the ISP one? Then you can flash whatever firmware you want on it and you can run the openvpn/wireguard client at the router level. You won't need to combine the Pi with it.